1. Field of the Invention
The present invention relates to a method of preparing a catalyst used for producing methacrylic acids through gas phase catalytic oxidation of methacrolein with molecular oxygen.
2. Description of the Related Art
Many proposals have been made on the methods and catalysts for producing methacrylic acids through gas phase catalytic oxidation of methacrolein. Especially, ever since discovery of the heteropoly-acid type catalysts, a number of patent applications have been filed regarding the improvements thereof. For example, catalysts containing germanium are disclosed in JP-A-57-45130 and JP-A-62-175435. However, the results of the reactions using the germanium-containing catalysts disclosed in the above patents are still unsatisfactory, and further improvements are required of such catalysts for their industrial use.